Compact cooling device

ABSTRACT

A cooling device for a chip in a portable computer that uses a horizontal flat fan in the corner of a portable computer housing with air outlets through heatsinks that enhance exhaust air flow over heat pipes from the chip and out through the computer housing. The exhaust is through the adjacent vertical walls of the computer housing. Separate heat pipes go directly from the chip to fins located at the outlet at the wall.

FIELD OF THE INVENTION

The invention is in the field of heat dissipation in portable electronicapparatus such as laptop computers where size, weight, and powerconsumption are constrained and in particular to heat transfer andcooling of heat produced in semiconductor chips used in such electronicapparatus.

BACKGROUND

The power consumption of laptop computers, especially the power ofCentral Processing Units (CPUs) such as semiconductor chips used inthem, is increasing. For instance, the total power of a laptop computerthat was usually in the range of 10 watts, now is around 50 watts. TheCPU power has been increased from 2 to about 18 watts and in the futureit could reach 40 watts. Most of this power will be dissipated as heatto the surroundings. Getting more heat out of a laptop computerefficiently is becoming urgent.

RELATION TO THE PRIOR ART

Although the idea of transferring heat from one place to another fordissipation is well known, the ability to transfer is constrained in theportable computer type of apparatus by the type of housing generallyemployed which is a shallow base with a hinged upper portion and by theair flow in that housing. There has been some work in the art as may beseen in the following documents.

In U.S. Pat. No. 6,105,662, titled “Cooling System for ElectronicPackages”, there is taught a cooling system including a heat radiator orheat sink connected to a heat conducting plate by means of a particulartube-like heat conducting element for heat transfer.

In U.S. Pat. No. 6,111,748, titled “Flat Fan Heat Exchanger and UseThereof in a Computing Device”, there is taught a fan heat exchangerincluding one type of flat fan that has air coming in from one side andexiting to the opposite side of the fan housing at the same level. Thepatent shows several fan types in moving air guided with fins, in atypical computer housing.

There is developing a need in the art to move larger amounts of air inorder to carry the ever increasing heat from the CPU chip or chips tothe outside of the computer housing.

SUMMARY OF THE INVENTION

A cooling device for a portable computer is provided that uses a flatfan having air inlet capability into the fan housing near the propellershaft of the fan and having dual air outlets through the fan housing, incombination with dual finned heat sink exhaust air outlets through thecomputer housing. Each exhaust air outlet through the computer housingbeing independently connected via a separate heat pipe to the relativelyphysically small heat source of the computer such as a semiconductorchip. The air outlets and heat sinks exhaust through the adjacentvertical walls of the computer housing producing a situation where inputair comes into the fan housing parallel to, and exits perpendicularto,the shaft or axis of the fan. Each air outlet heatsink combination isprovided with fins that together with position enhance volume of airflow. The heat from the chip is thus conveyed for transfer into theexhaust air at the exit point from the computer housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective depiction of the elements of the inventionpositioned at an intersection of housing walls in a laptop computer.

FIG. 2 is a top view of the flat fan assembly combined with the finnedheatsink air outlets.

FIG. 3 is a cross-sectional view of the flat fan of the inventionillustrating the air inlets and air outlets.

FIGS. 4 a and 4 b are top and side view depictions respectively for anend of a heat pipe passing through a fin assembly.

FIG. 5 is a side view depiction of the assembly of the separate heatpipes in contact with a single heat generating source such as asemiconductor chip on a printed-wiring board.

FIG. 6 is a perspective depiction of connection blocks use in retainingan end of a heat pipe.

DESCRIPTION OF THE INVENTION

Referring to FIG. 1 a perspective depiction is provided of the elementsof the invention positioned at an intersection of housing walls in alaptop computer and to FIG. 2 which is a top view of the flat fanassembly combined with the finned heatsink air outlets. The base 1 ofthe computer has intersecting walls 2 and 3 and a hinged display member4.

The flat fan assembly 5 is in a horizontal position at the intersectionof the walls 2 and 3. The assembly 5 has air inlets 6 A on the upperside, which is shown removed in FIG. 2, and 6B on the lower side. Theflat fan assembly 5 further has air outlet regions 7 A and 7B that arenot visible in FIG. 1, and are separated around the periphery of the fanassembly 5 in FIG. 2. The regions 7A and 7B are each in a combinationwith air flow enhanced heat sink members 8 and 9, and in turn are eachindependently connected via separate heat pipes 10 and 11 to aphysically small heat source 12 such as a semiconductor chip, locatedunder the ends of the heat pipes 13 and 14 not visible in this figure,and mounted on a substrate board 15. The air inlets 6A and 6B, are nearthe axis 16 of the fan assembly 5. The structure of FIGS. 1 and FIG. 2produce a situation where input air comes into the fan assembly 5parallel to, and exits perpendicular to, the axis 16 of the fan.

Each heatsink member 8 and 9 is provided with fins that enhance airflow. The fins are not visible in FIG. 1 and are labelled 40 and 41 inFIG. 2. The heat is conveyed through the separate heat pipes 10 and 11from the chip 12 to the separate heatsinks 8 and 9 so that the heatpipes 10 and 11 each transfers all heat at the exit, 40 through wall 3,41 through wall 2, of the computer housing. A clamping mechanism 18 inFIG. 1 is used to hold the two heat pipe ends 13 and 14 in good thermalcontact with the chip package. The structural details of the compactcooling device are further shown in FIG. 2 which is a top view of theflat fan assembly 5 in combination with the finned heatsink air outlets8 and 9. Considering the structure and operation of the invention inFIG. 2, which is the flat fan housing 5 of FIG. 1 with the covercontaining air inlets 6A removed permitting viewing inlets 6B.

The housing 5 has portions 21 and 21A that hold the parts containing theair inlets 6A and 6B apart and define the air outlet openings 7A and 7B.The shaft 23 holds the fan motor 22, not shown. Numerous fan blades 24are attached to the shaft 23. With counter clockwise rotatation theoutgoing air, as indicated by the arrows labelled 25 moves at highervolume where the air outlet heatsinks 8 and 9 are at less than the rightangle of the computer housing walls 2 and 3.

It will be apparent that the shape of the fan housing 5, the number ofthe fan blades 24, and the number of openings at the air inlets 6A and6B are exemplary and should not be limited to those shown in the figure.The construction of the fins 40 and 41 of the invention are arranged formaximum air flow volume enhancement, they vary in length and distanceapart and the fin assemblies depart from being perpendicular to thesides 2 and 3 in the direction of tangency to the air flow 25 directionin the fan.

Referring to FIG. 3 where the fan in the housing 5 of FIGS. 1 and 2 isshown in cross section in FIG. 3. along the dotted line 3-3 in FIG. 2.The motor and motor shaft 23 is in the center. The majority of theelectronics to drive the motor is associated with the shaft 23. The airinlets 6A are through the upper cover and the air inlets 6B are throughthe lower cover. The air outlets 27 and 28 direct air output through tothe heatsinks 8 and 9 as directed by elements 21 and 21A, out of view inFIG. 3.

Referring to FIG. 4 there are side and top view depictions labelledFIGS. 4A and 4B respectively showing the end of the heat pipe 11 showndotted in FIG. 2, passing through the fin assembly 40 of heatsink 8. Thestructure of the two air heatsink outlets 8 and 9 are identical inprinciple as depicted in FIG. 2. As indicated in the side view of theair outlet heatsink 8 in FIG. 4 a, one end of the heat pipe 11 isinserted at its main body with numerous fins 40 protruded outward. Theair outlet heatsink 8 and its fins 40 are made of thermally conductivematerials such as aluminum or copper. A cover 45 surrounding the fins 40to protect the fins and guide the air flow may be provided. Asillustrated in FIG. 4B the spacing 46 between the fins varies accordingto the length of the fins. Further, as illustrated in both FIG. 2 andFIG. 4 the fin length varies to conform with the shape of the fan outlet27.

Referring to FIG. 5 there is shown a side view of the clamping mechanismto bring the heat pipes in contact with the heat generatingsemiconductor chip 12. The semiconductor chip 12 is soldered on aprinted-wiring board 52. The two connection blocks 13 and 14 with heatpipes 10 and 11 inserted within are placed on the top of thesemiconductor chip 12. The connection blocks are forced into a goodthermal contact with the chip 12 by two elastomer or spring pieces 50using a clamp 51 which is anchored on the printed-wiring board 52.

The heat pipe structures lend themselves to variety of arrangements. Asshown in FIG. 6, the connection block 55 consists of two pieces. One endof the connection block piece has a trough-like cut 56. The heat pipe 10is inserted into the two connection block pieces with the trough-likecuts facing each other. The two connection block pieces are separated bya clearance 57. The dimension of the trough-like cut is made larger thanthe diameter of the heat pipe such that there is a free space 58 underand around the heat pipe within the cut 56. The two connection blockpieces pick up the heat from the semiconductor chip and conduct it tothe heat pipe. This two-piece structure of the connection block providesa certain degree of the freedom for the connection blocks to make acompliant contact with the surface of the semiconductor chip. A reliableand efficient thermal contact is therefore ensured. The thermal contactcan be improved further if the spaces between the block pieces and thespaces within the trough-like cut in the block pieces are filled withthermally conductive fluid-like or gel-like materials such as thermalpastes.

What has been described is device principle for heat dissipation inportable electronic apparatus such as laptop computers where size,weight, and power consumption are constrained.

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 10. In portablecomputing apparatus of the type that is powered by a central processingunit of relatively small size, such as a semiconductor chip, positionedin housing including a base portion with vertical walls enclosing anessentially rectangular base area member, the method of improvement ofheat transfer comprising in combination the steps of: positioning, a fanof the flat type having an impeller rotatable in a circular housing andpositioned on a shaft where the impeller rotation is perpendicular tosaid shaft, at a location in said base portion at an intersection of afirst and second of said vertical walls and each of said intersectingwalls has a location that is in a tangential relationship to saidcircular housing, modifying said fan housing so that input air enterssaid housing in the vicinity of said shaft and is forced out of firstand second exhaust openings in said housing that coincide with saidtangential relationship locations of said first and second walls whensaid impeller rotates, providing first and second air exhaust openingsthrough said vertical walls of said computer base portion at saidtangential relationship locations, and, providing an air flow enhancingexhaust air conduit between said exhaust openings in said fan housingand said exhaust openings through said vertical walls of said computerbase portion.
 11. The method of heat transfer improvement of claim 10wherein said step of air flow enhancement step includes positioning offins in said exhaust openings.
 12. The method of heat transferimprovement of claim 11 including the step of providing heat pipethermal transfer capability from said central processing unit in saidbase portion to said exhaust openings through said vertical walls ofsaid computer base portion.
 13. The method of heat transfer improvementof claim 10 includes enhancement of exhaust air heat transfer involvesadjustments selected from the group of fin spacing and heat pipepositioning.
 14. The method of heat transfer improvement of claim 12including the step of providing said heat pipe thermal transfercapability from said central processing unit in said base portion to andthrough each of said fins.
 15. The method of heat transfer improvementof claim 14 including the step of providing thermal attachment of afirst end of said heat pipe to said central processing unit in said baseportion and the remaining end of said heat pipe to said fins.
 16. Themethod of heat transfer improvement of claim 15 including the step ofproviding a separate heat pipe extending from said central processingunit to each said exhaust 3 opening.
 17. The method of heat transferimprovement of claim 16 including the step of providing a separate heatpipe extending from said central processing unit to each said exhaustopening and into thermal contact with each fin in said opening. 18.Cooling apparatus for a portable computer powered by a chip, saidcomputer being of the type with an outside vertical wall housing withinwhich there is a fan housing with intersecting vertical walls enclosingan essentially rectangular base area member and within which there is afan structure with fan blade members attached to a vertical shaft memberthat rotate with said shaft, and an air outlet heat sinking openingthrough said fan housing and extending through said outside housing, animprovement comprising in combination: the positioning of said fanhousing at an intersection of the walls of said outside housing,whereby, air volume enhancement fins positioned in a heatsinking housingopening, can extend through both said fan housing and said outsidehousing walls, the positioning of air inlet openings through the coversaround the location of said shaft member, whereby all vertical wallsbecome available for air outlet openings, and, whereby a heat sinkingopening through to the outside occurs as the shaft turns and theopenings become aligned.
 19. Cooling apparatus for a portable computerpowered by a chip, said computer being of the type having a base housingwith first and second intersecting vertical walls enclosing anessentially rectangular area, the improvement comprising in combination:an air outlet opening through each of said first and second base housingintersecting vertical walls, a fan structure of the type having, a fanhousing with intersecting fan housing vertical walls supporting top andbottom cover members, and having an air output opening through eachintersecting vertical wall. a vertical shaft member positioned in saidfan housing extending between said top and bottom covers with fan blademembers attached to said shaft member that rotate with said shaft, saidfan structure being positioned with said intersecting fan housingvertical walls within the intersection of said base housing verticalwalls, an air input opening through at least one of said top and bottomcovers near said shaft, first and second air output finned heat sinkmembers each positioned in an air outlet opening in said base housingand extending into a corresponding opening in a vertical wall in saidfan housing, and, first and second heat pipe thermal transfer membersthermally attached to each fin of said heat sink members and to saidchip.